physiology 3 renal Flashcards
Filtered sodium is about
26000 mmol/day
mmol of Na+ excretion is excreted in urine each day.
150 mmol
how much of the filtered Na reabsorbed?
99.50%
Does the filteration fraction with an increase in sodium
nope
What increases with an increas in sodium intake
RPF and GFR + excretion of sodium
a decrease in sodium intake increases
FF
Which decreases more? The RPF or GFR?
RPF
The ability of the tubules to increase reabsorption rate in response to increased GFR and tubular load.
glomerutubular balance
This balance minimizes the effect of changes in GFR and prevents overloading of tubules.
purpose of glomerutubular balance
The proximal tubule tends to reabsorb a constant proportion (65%) of the glomerular filtrate rather than a constant amount.
just know it.
eflex vasoconstriction or dilatation of afferent arteriole in response to changes in tubular flow.
Tubulo-glomerular feedback
Funtion of TGF
Increased flow rate in late ascending limb of loop of Henle and first part of distal convoluted tubuleàdecreases GFR (decreased flow increases GFR)
ThesensorforTGFisthe
macula densa
High flow rate and high NaCl in the macula densa results in
release of substances like (ATP) à generate adenosine, a potent vasoconstrictor of afferent arteriole àdecrease GFR.
which substances enhance TGF, and which blunt it
angio 2 + ROS enahnce, NO blunts
what increases when increase when renal arterial pressure increases.
sodium and water excretion
entral component in the long term regulation of arterial blood pressure.
pressure natriuresis
Sympathetic nerve terminals affect sodium reabsorption in the kidney by
releasing norepinephrine (NE) which decreases Na+ and water
what does renin do?
– Increasedsympathetictone.
– Decreasedrenalperfusion(lessstretch). – Decreased delivery of NaCl to macula
densa (Hyponatremia).
Renin release is inhibited by
angi2
converts angiotensinogen to angiotensin I (AI).
renin
angio 2 stimulates 2 transporters, name them
Direct stimulation Na+ reabsorption in most parts of the renal tubules (activate Na-K pump).
• Direct stimulation of Na+-H+ antiporter in proximal tubules.
Aldosterone increases Na+ reabsorption, how?
– Rapid:increasestheactivityofpre-existing
ENaCs and Na-K ATPase.
– Late:increasesnumberofapicalNa+
channels and basolateral Na-K pumps.
Excess aldosterone causes
hypokalemia
and increases ECF volume and BP
ANP release is stimulated by
atrial distension due to volume expansion
– Directly increases GFR via afferent arteriolar
dilation and efferent constriction.
– Inhibits renin and aldosterone secretion.
– Inhibits Na+ reabsorption in deep medullary collecting ducts.
– Increases Na+ and water excretion.
actions of ANP
• Formed locally in the kidneys from circulating L-dopa.
dopamine
– In low doses causes renal vasodilatation and increases Na+ excretion.
– Increases sodium excretion by diminishing reabsorption in the proximal tubule and collecting tubule.
– DirectlyinhibitsapicalNa-Hexchanger and basolateral Na-K pump primarily in the proximal tubule.
actions of dopamine
It inhibits Na+ reabsorption through ENaCs, autocrine function on the collecting ducts
endothelin
inhibits Na+ reabsorption in the thick ascending limb and collecting ducts, produced locally in the kidney
prostaglandins
